chr2-178624687-C-T

Position:

• chr2-178624687-C-T

Variant summary

Our verdict is Likely benign. Variant got -4 ACMG points: 1P and 5B. PP2 BP4_Strong BP6

The NM_001267550.2(TTN):​c.44593G>A​(p.Glu14865Lys) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000571 in 1,612,410 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.00017 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000045 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:6 B:5
• Conservation: PhyloP100: 7.86

Genes affected

TTN (HGNC:12403): (titin) This gene encodes a large abundant protein of striated muscle. The product of this gene is divided into two regions, a N-terminal I-band and a C-terminal A-band. The I-band, which is the elastic part of the molecule, contains two regions of tandem immunoglobulin domains on either side of a PEVK region that is rich in proline, glutamate, valine and lysine. The A-band, which is thought to act as a protein-ruler, contains a mixture of immunoglobulin and fibronectin repeats, and possesses kinase activity. An N-terminal Z-disc region and a C-terminal M-line region bind to the Z-line and M-line of the sarcomere, respectively, so that a single titin molecule spans half the length of a sarcomere. Titin also contains binding sites for muscle associated proteins so it serves as an adhesion template for the assembly of contractile machinery in muscle cells. It has also been identified as a structural protein for chromosomes. Alternative splicing of this gene results in multiple transcript variants. Considerable variability exists in the I-band, the M-line and the Z-disc regions of titin. Variability in the I-band region contributes to the differences in elasticity of different titin isoforms and, therefore, to the differences in elasticity of different muscle types. Mutations in this gene are associated with familial hypertrophic cardiomyopathy 9, and autoantibodies to titin are produced in patients with the autoimmune disease scleroderma. [provided by RefSeq, Feb 2012]

TTN-AS1 (HGNC:):

ACMG classification

Verdict is Likely_benign. Variant got -4 ACMG points.

• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), TTN. . Gene score misZ -1.1021 (greater than the threshold 3.09). Trascript score misZ 6.9794 (greater than threshold 3.09). GenCC has associacion of gene with dilated cardiomyopathy, tibial muscular dystrophy, early-onset myopathy with fatal cardiomyopathy, autosomal recessive centronuclear myopathy, hypertrophic cardiomyopathy, hypertrophic cardiomyopathy 9, TTN-related myopathy, dilated cardiomyopathy 1G, arrhythmogenic right ventricular cardiomyopathy, myopathy, myofibrillar, 9, with early respiratory failure, familial isolated dilated cardiomyopathy, childhood-onset progressive contractures-limb-girdle weakness-muscle dystrophy syndrome, autosomal recessive limb-girdle muscular dystrophy type 2J.
• BP4: Computational evidence support a benign effect (MetaRNN=0.036146373).
• BP6: Variant 2-178624687-C-T is Benign according to our data. Variant chr2-178624687-C-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 229437.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=3, Uncertain_significance=6, Benign=2}. Variant chr2-178624687-C-T is described in Lovd as [Likely_benign].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2	c.44593G>A	p.Glu14865Lys	missense_variant	242/363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.44593G>A	p.Glu14865Lys	missense_variant	242/363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes AF: 0.000171 AC: 26 AN: 151924 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000985

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00117

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000736

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.000125 AC: 31 AN: 247764 Hom.: 0 AF XY: 0.0000967 AC XY: 13 AN XY: 134430

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.000233

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00101

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000446

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000452 AC: 66 AN: 1460368 Hom.: 0 Cov.: 32 AF XY: 0.0000440 AC XY: 32 AN XY: 726466

Gnomad4 AFR exome AF: 0.0000599

Gnomad4 AMR exome AF: 0.000157

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.000506

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000333

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.000171 AC: 26 AN: 152042 Hom.: 0 Cov.: 32 AF XY: 0.000202 AC XY: 15 AN XY: 74328

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.000984

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00117

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000736

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000113 Hom.: 0

Bravo AF: 0.0000982

ExAC AF: 0.000132 AC: 16

Asia WGS AF: 0.000867 AC: 3 AN: 3476

EpiCase AF: 0.0000546

EpiControl AF: 0.00

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:6 Benign:5

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not specified Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Jul 08, 2015	Variant classified as Uncertain Significance - Favor Benign. The p.Glu12297Lys v ariant in TTN has not been previously reported in individuals with cardiomyopath y but has been identified in 0.15% (13/8394) East Asian chromosomes by the Exome Aggregation Consortium (ExAC, http://exac.broadinstitute.org). Computational pr ediction tools and conservation analyses do not provide strong support for or ag ainst an impact to the protein. In summary, while the clinical significance of t he p.Glu12297Lys variant is uncertain, its frequency suggests that it is more li kely to be benign. -
Uncertain significance, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Sep 22, 2023	Variant summary: TTN c.36889G>A (p.Glu12297Lys) results in a conservative amino acid change located in the I band region of the encoded protein sequence. Two of four in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 0.00013 in 247764 control chromosomes. To our knowledge, no occurrence of c.36889G>A in individuals affected with Limb-Girdle Muscular Dystrophy, Type 2J and no experimental evidence demonstrating its impact on protein function have been reported. Six submitters have cited clinical-significance assessments for this variant to ClinVar after 2014 and classified the variant as VUS (n=2) and benign/likely benign (n=4). Based on the evidence outlined above, the variant was classified as uncertain significance. -

not provided Uncertain:1 Benign:1

Likely benign, criteria provided, single submitter	clinical testing	GeneDx	Jun 03, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Jun 08, 2023	- -

Autosomal recessive limb-girdle muscular dystrophy type 2J Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Dilated cardiomyopathy 1G Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Early-onset myopathy with fatal cardiomyopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 08, 2024

- -

Cardiomyopathy Benign:1

Likely benign, criteria provided, single submitter

clinical testing

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

Apr 14, 2021

- -

Tibial muscular dystrophy Benign:1

Benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

Myopathy, myofibrillar, 9, with early respiratory failure Benign:1

Benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.30
BayesDel_addAF	Benign	-0.26	T
BayesDel_noAF	Benign	-0.20
CADD	Uncertain	24
DANN	Uncertain	0.99
Eigen	Uncertain	0.45
Eigen_PC	Uncertain	0.53
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.93	D;D;D;.;D;D;D
M_CAP	Benign	0.055	D
MetaRNN	Benign	0.036	T;T;T;T;T;T;T
MetaSVM	Benign	-0.68	T
MutationAssessor	Benign	0.38	.;.;.;N;.;.;N
PrimateAI	Uncertain	0.76	T
PROVEAN	Uncertain	-2.6	D;D;.;.;D;D;.
REVEL	Uncertain	0.37
Sift	Benign	0.098	T;D;.;.;D;D;.
Polyphen		0.99	.;.;.;D;.;.;D
Vest4		0.60
MutPred		0.56		.;.;.;Gain of ubiquitination at E13224 (P = 0.0146);.;.;Gain of ubiquitination at E13224 (P = 0.0146);
MVP		0.32
MPC		0.29
ClinPred		0.13	T
GERP RS		5.0

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs543102139; hg19: chr2-179489414;